The present invention relates to apparatuses for processing radioactive wastes, and more exactly to an installation for vitrification of liquid homogeneous/heterogeneous radioactive wastes, including those comprising ion-exchange resins, and also to a cooled discharge unit and a cooled induction melter for that installation.
The invention may be used for hardening liquid radioactive wastes by transferring them into a solid stable vitriform state suitable for long-term storage in special storages.
An apparatus is known for supplying different fractions of material (see, for example, U.S. Pat. No. 3,964,892, 1976), comprising a metal housing having a flat bottom, a refractory reflector positioned on the inner surfaces of the metal housing and the flat bottom, a tubular channel for discharge of the melt which is positioned in the flat bottom and has a reduced inlet aperture which is closed by means of a rod which controls the output of glass melt, electrodes positioned at an angle of 120 degrees, a coil-in-box cooler positioned on the external side of the upper part of the metal housing, a charging device and a turning-positioning mechanism for the rod.
The danger of operation with the apparatus is high because of the high chemical corrosion of the electrodes and the refractory reflector. The durability of the apparatus is low because of the burn-out of the electrodes and the short service life of the refractory reflector, Furthermore, during the discharge there is the danger of the occurrence of an emergency situation due to the danger of the tubular channel overheating, of its higher chemical corrosion due to the unguaranteed closure of its reduced inlet aperture because of the higher chemical corrosion of the rod and the tubular discharge channel, and also because of the danger of the formation of a hard-to-remove glass plug in the tubular discharge channel.
A Joule melter is known for processing radioactive wastes (see, for example, Europatent 0 137 579, 1985), comprising a steel casting closed at the top by a steel lid, the inner surface of which is lined with a refractory material. A jumper is positioned on the bottom part of the refractory material, an electrode of cylindrical shape is positioned around the jumper, wherein a partition of cylindrical shape having an aperture is positioned inside the electrode, while a starting heater is positioned on the external side. An outlet pipe for the discharge of glass melt is located in the center of the bottom part, this pipe being simultaneously a second electrode and with its upper part being covered by a truncated cone with an aperture. A pipe of large diameter for the discharge of waste gases, an inlet pipe for loading the radioactive wastes and vitrification agents, and also a movable plunger with a conical end-piece ensuring closure of the aperture of the truncated cone are positioned in the steel lid.
Due to the burn-out of the electrode of cylindrical shape, which is a part of the melter housing, and of the second electrode, which is an outlet pipe for the discharge of the glass melt, and also due to the higher carrying away of radio nuclides, there is high danger in the operation of the melter.
Since the jumper has a reduced, temporary service life, the durability of melter operation is also low. And due to the greater amount of time necessary to create a starting melt by means of the starting heater, the productivity is low.
This melter has a narrow field of use due to the fact that it is not possible to process dehydrated radioactive wastes which contain ion-exchange resins which during melting may plug the uncooled inlet pipe for loading, or to process moist radioactive wastes which contain ion-exchange resins which may cause short circuiting of the electrodes through the moist radioactive wastes which are on the surface of the glass melt.
The danger of the occurrence of an emergency situation during discharge is also present in the aforesaid melter due to the blocking up of the outlet pipe for the discharge of melt, the impossibility of clearing it with a plunger, the danger of its overheating, high chemical corrosion, and also its burning out.
A method and apparatus for vitrification of radioactive materials is known (see, for example, British patent 1, 239 710, 1971). The apparatus for vitrification of radioactive materials is a crucible provided with a cooling system and with an induction coil connected to a high frequency generator. On top the crucible is closed with a metal lid with apertures to which a calciner and a bunker with vitrification agents, which is provided with a vibrating feeder, are connected. There is a discharge device at the bottom of the crucible which is a discharge pipe provided with a water-cooled jacket and an inductance coil connected to a high frequency generator.
There is a high degree of danger during operation of the apparatus due to high chemical corrosion of the housing of the crucible, the danger of its mechanical breakdown in the presence of high thermal stresses caused by a large difference between the temperature on the outer and inner surfaces, and also due to an increase in the degree of votalization of radio nuclides due to the use of a calciner for calcinating radioactive materials.
Furthermore, the melter has reduced productivity due to the absence of a mixer for preliminary mixing of the calcinate of radioactive materials and the vitrification agents, and also due to the immobility of the inductance coil of the crucible.
The field of use of the apparatus is also limited due to the fact that it is not possible to process ion-exchange resins which due to their melting in the calciner will plug the inlet pipe for loading the calcinate of radioactive materials.
During the discharge an emergency situation may arise since there is no discharge gate and this may be the reason for unauthorized discharge of the glass melt from the crucible.
The object of the present invention is to create an installation for vitrification of liquid homogeneous and heterogeneous radioactive wastes which may include ion-exchange resins, and also radioactive pearlite, activated carbon, sand, in which the use of a water-cooled induction melter with a cooled discharge unit and a movable inductor, of an evaporator for dehydrating liquid radioactive wastes, of a vortex apparatus and a separate system for purification of gas make it possible to carry out the processing of radioactive wastes with minimum contamination of the environment, eliminating the discharge of radioactive gaseous and dust-like substances into the atmosphere, to raise the safety of operation of the device, its reliability and productivity, and also to expand the field of use of the device, ensuring the possibility of processing radioactive wastes which have different compositions.
Another object of the invention is to create a cooled discharge unit for the water-cooled induction melter, the construction of which would make it possible to eliminate unauthorized discharge of the vitriform melt from the induction melter, to ensure reliable closure of the discharge unit after discharge, to avoid overheating of the housing of the discharge unit and to accomplish constant reliable cooling of all the elements of the discharge unit, which in turn makes it possible to eliminate the occurrence of emergency situations during discharge and to enhance the durability.
One more object of the invention is to create a water-cooled induction melter in which the use of a cooled discharge unit and also a movable inductor makes it possible to accomplish the processing of moist radioactive wastes and to increase the productivity of the apparatus.
The aforesaid object is achieved in that a cooled discharge unit in accordance with the invention comprises
a discharge pipe,
a cooling jacket having a U-shaped form in cross section and disposed on said discharge pipe,
a lid covering said cooling jacket and said discharge pipe,
a lug in the form of a truncated cone made in said lid from the side facing the discharge pipe,
a through cylindrical aperture made in said lug, a longitudinal axis of which coinciding with a longitudinal axis of said discharge pipe,
a group of apertures made in said lid and serving to remove a coolant from said cooling jacket,
a collector for feeding the coolant into the jacket and positioned on said jacket from the side opposite said lid,
a group of apertures made in said collector for supplying the coolant to said cooling jacket,
a discharge gate comprising a pipe, on one end of which, facing said lug, is Positioned a cone-shaped tip, on the other end a lid with an aperture, adjacent which is positioned a pipe for discharge of the coolant,
a pipe for supplying the coolant, positioned coaxially with said pipe of the discharge gate in said aperture of the lid, one end of which being positioned adjacent the cone-shaped tip, another end protruding outside said lid.
It is advisable that the cone-shaped tip be made of one piece and consist of
a first truncated cone having a large base and a smaller base and being rigidly secured by the large base to said pipe of the discharge gate,
a second truncated cone having a large base and a smaller base, wherein the large base of said second truncated cone is the smaller base of said first truncated cone,
a third cone having a base which is the smaller base of said second truncated cone.
It is advantageous that said first truncated cone and second truncated cone be made hollow.
It is preferable that the longitudinal axis of said discharge pipe be shifted toward a round portion of said U-shaped jacket.
The stated object is also achieved in that the induction melter, in accordance with the invention, comprises
a housing side walls and bottom of which are made of metal pipes disposed with a gap relative to each other and combined by a collector for supplying and discharging a coolant,
a hollow cooled lid provided with pipes for supplying and discharging the coolant,
pipes for loading a mixture of liquid radioactive wastes and vitrification agents, pipes for discharge of waste gases, pipes for returning filtrate and a port for technological servicing positioned in said lid,
a bushing positioned in said lid, the geometrical axis of which is parallel to the axis of said housing and the length of which is somewhat greater than the thickness of said lid,
a discharge gate positioned in said bushing and provided with a drive for vertical displacement,
at least one pipe for positioning sensors of technological parameters of the process,
an inductor positioned adaptable for displacement along the longitudinal axis of said melter and concentrically encompassing said side walls of the housing, the gaps between the pipes of which ensuring transparency of the housing for an electromagnetic field of the inductor, the short inductor serving to create maximum magnetic field strength directly adjacent the moving surface of a melt produced during the input and melting of the mixture of liquid radioactive wastes and the vitrification agents,
a means for moving said inductor along the longitudinal axis of said melter,
an aperture in said bottom of the housing directly adjacent said wall,
a cooled discharge unit positioned in said aperture, the height of said cooling jacket of said discharge unit determining the minimum melt level, a portion of said cooling jacket being a part of the side wall of the housing and another portion of said cooling jacket facing the melt.
It is advisable that said pipe for discharge of waste gases contain a cooling jacket.
It is useful that said port for technological servicing be provided with a cooled lid.
It is advantageous that sensors selected from the following group be used as sensors of technological parameters: at least two melt surface temperature sensors, a sensor of the pressure of gases above the melt surface, a sensor of the temperature of gases above the melt surface, and a picture monitor.
The object is also achieved in that an installation for vitrification of liquid radioactive wastes, in accordance with the invention, comprises
a mixer provided with a means for mixing components, having an input, a second input, and an output,
a doser of vitrification agent additives, having an output coupled to said input of said mixer,
a doser of heterogeneous liquid radioactive wastes, connected by its output to said second input of said mixer,
a vessel-accumulator provided with a means for homogenization of components, having an input coupled to said output of said mixer and an output,
a vortex apparatus serving to process the mixture of liquid radioactive wastes in a vortex layer, having an input connected to said output of said vessel-accumulator, and an output provided with a doser,
a cooled induction melter with a movable inductor, having a first input connected to said output of said doser of the vortex apparatus, a second input, a first output for discharge of obtained melt of vitrified radioactive wastes and a second output for discharge of waste gases,
a means for filtering waste gas having successively mounted coarse filters and fine filters, having an input connected to said second output of said melter, and an output,
a condenser for condensing liquid vapors released from said melter, having an input connected to said output of said means for filtering waste gas and an output,
a means for capturing gaseous toxic components, including an absorber, heater, catalytic reactor and condenser, and having an input coupled to an output of said condenser, and an output coupled to the atmosphere.
The object is also achieved in that an installation for vitrification of liquid radioactive wastes, in accordance with the invention, comprises
a vessel for receiving a dosed portion of homogeneous liquid radioactive wastes and collecting concentrated homogeneous liquid radioactive wastes, the vessel being linked to a collector of liquid radioactive wastes and having first and second inputs and an output,
an evaporator having an input, provided with a gate and coupled to said output of said vessel to receive radioactive wastes, and having a first output coupled to second input of said vessel to receive radioactive wastes, and a second output,
a separator for separating droplets of liquid from the steam-gaseous mixture, having an input connected to said second output of said evaporator, and having an output,
a condenser for condensing steam having an input coupled to said output of said separator, and an output for the discharge of a condensate,
a mixer provided with a means for mixing components, having an input provided with a gate and connected to said output of said vessel to receive concentrated homogeneous liquid radioactive wastes, a second input, third input and output,
a doser of vitrification agent additives, having an output coupled to said second input of said mixer,
a doser of heterogeneous liquid radioactive wastes, connected by its output to said third input of said mixer,
a vessel-accumulator provided with a means for homogenization of components, having an input coupled to said output of said mixer and an output,
a vortex apparatus serving to process the mixture of liquid radioactive wastes in a vortex layer, having an input connected to said output of said vessel-accumulator, and an output provided with a doser,
a cooled induction melter with a movable inductor, having a first input connected to said output of said doser of the vortex apparatus, a second input, a first output for discharge of obtained melt of vitrified radioactive wastes and a second output for discharge of waste gases,
a means for filtering waste gas having successively mounted coarse filters and fine filters, having an input connected to said second output of said melter, and an output,
a second condenser for condensing liquid vapors released from said melter, having an input connected to said output of said means for filtering waste gas and an output,
a means for capturing gaseous toxic components, including an absorber, heater, catalytic reactor and condenser, and having an input coupled to an output of said second condenser, and an output coupled to the atmosphere.
It is advisable that said coarse filter be coupled to said water-cooled induction melter.